Protective film for glass

ABSTRACT

A glass protecting film including at least 5 or more layers, of which at least one layer is the layer which comprises polyester having 1,4-cyclohexane dimethanol is one of the components, and a glass protecting including a multi-layer structure which comprises at least two kinds of thermoplastic resin, of which the difference of glass transition temperature is 40° C. or less, the face-impact strength is 18 J/mm or more, haze is 3% or less, are films which excel in transparency, tear resistance, and impact resistance, and are suitable for protecting glass and preventing damaged glass fragments.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. Ser. No. 10/494,214 filed May3, 2004 U.S. Pat No. 7,241,485, which is a §371 of PCT/JP02/11148 filedOct. 28, 2002 which claims priority of Japanese Application No.2001-344432 filed Nov. 9, 2001 and Japanese Application No. 2001-379895filed Dec. 13, 2001.

TECHNICAL FIELD

This disclosure relates to a glass protecting film, and moreparticularly relates to a glass protecting film suitable for protectingdisplay glass such as a CRT display, liquid crystal display, plasmadisplay, organic EL display, field emission display, and the like, orwindow glass for automobiles, HST (High-Speed Trains), electric trains,structures such as public facilities, general houses, larger buildings,and the like.

BACKGROUND

In general, glass has been employed for various kinds of purposes, owingto excellent light transmittance, gas barrier properties, dimensionalstability, and so forth. Glass has been employed not only forwindowpanes for buildings, automobiles, and trains, but also for flatdisplays in which high-performance glass is employed, represented by CRTdisplays, liquid crystal displays, plasma displays, organic EL displays,field emission displays, and so forth. However, glass has disadvantagessuch as easily breaking and scattering upon breaking. This problem ismarked in the flat display field where there is great demand forreducing the thickness of glass. As the thickness of the entire flatdisplay is reduced, the display glass employed therein has been reduced,leading to a problem that glass is easily broken at the time of the flatdisplay being used.

Various kinds of proposals have been made for preventing glass frombreaking and scattering due to breaking, by applying a film formed ofthermoplastic resin onto the glass.

For example, Japanese Unexamined Patent Application Publication No.6-190997 discloses that applying a multi-layer laminated film formed ofa polyethylene terephthalate layer and a sebacic acidcopolymerization—polyethylene terephthalate layer onto the surface ofglass can markedly prevent glass from damage and scattering.

However, while the method according to Japanese Unexamined PatentApplication Publication No. 6-190997 has effects to prevent glass fromscattering, on the other hand, this causes crystallization andconsequently a hazy appearance over time, since the glass transitiontemperature of the sebacic acid copolymerization—polyethyleneterephthalate layer forming the multi-layer laminated film is low,thereby bringing about a state wherein transmission of visible lightdeteriorates. In addition, while the method according to JapaneseUnexamined Patent Application Publication No. 6-190997 improves tearresistance of a film, this has little effect on improving impactresistance and preventing the glass itself from breaking. Accordingly,the method according to Japanese Unexamined Patent ApplicationPublication No. 6-190997 cannot be employed for a glass protecting filmfor a flat display which requires continuous high transmittance ofvisible light and also needs to prevent glass damage itself.

SUMMARY

Our glass protecting films excel in transparency, tear resistance, andimpact resistance, and also is suitable for protecting glass andpreventing the scattering of broken fragments of glass.

Our glass protection films comprise at least 5 or more layers, of whichat least one layer is the layer which comprises polyester having1,4-cyclohexane dimethanol as one of the components.

Another form of our glass protection films is a glass protecting filmcomprising a multi-layer structure which comprises at least two kinds ofthermoplastic resin of which the difference in glass transitiontemperature is 40° C. or lower, in which face-impact strength is 18 J/mmor more, and in which haze is 3% or less.

DETAILED DESCRIPTION

First, a description will be made regarding a glass protecting filmaccording to a first aspect, which comprises at least 5 or more layers,of which at least one layer is the layer which comprises polyesterhaving 1,4-cyclohexane dimethanol as one of the components.

The glass protecting film according to the first aspect comprises atleast 5 or more layers, of which at least one layer is the layer whichcomprises polyester having 1,4-cyclohexane dimethanol as one of thecomponents.

The glass protecting film according to the first aspect needs tocomprise at least 5 layers or more.

The glass protecting film according to the first aspect needs tocomprise at least one layer which comprises polyester having1,4-cyclohexane dimethanol as one of the components.

“Polyester having 1,4-cyclohexane dimethanol as one of the components”is defined as polyester having, as one of the components, homopolyesterin which diol components thereof is 1,4-cyclohexane dimethanol, orcopolymer polyester in which diol components thereof is 1,4-cyclohexanedimethanol.

Polyester having 1,4-cyclohexane dimethanol as one of the components mayinclude, as the diol components, ethylene glycol, 1,2-propanediol,1,3-butanediol, 1,4-butanediol, 1,5-pentadiol, diethylene glycol,polyalkylene glycol, 2,2-bis (4′-β-hydroxyethoxyphenyl) propane, and thelike, besides the 1,4-cyclohexane dimethanol.

In the event of at least one layer containing polyester having1,4-cyclohexane dimethanol as one of the components, a layer whichcomprises polyester having 1,4-cyclohexane dimethanol, which excels inrigidity and impact absorption, as one of components, preventspropagation of cracking, caused by impact or tear. Consequently, impactresistance and tear resistance improve. Moreover, a layer whichcomprises polyester having 1,4-cyclohexane dimethanol as one of thecomponents has high transparency, and hardly ever becomes hazy at roomtemperature over time, so that an image can be precisely recognized indetail through the film.

Moreover, the glass protecting film according to the first aspectpreferably comprises 2 or more layers which comprises polyester having1,4-cyclohexane dimethanol as one of the components, and furtherpreferably comprises 3 or more layers.

The glass protecting film according to the first aspect preferablycomprises a layer which comprises thermoplastic resin, besides a layerwhich comprises polyester having 1,4-cyclohexane dimethanol as one ofthe components.

As for the thermoplastic resin which is preferably comprised in theglass protecting film according to the first aspect, for example,polyolefine resin such as polyethylene, polypropylene,polymethylpentene, and the like, polyamide resin such as nylon 6, nylon66, and the like, polyester resin such as polyethylene terephthalate,polybutylene terephthalate, polyethylene-2,6-naphthalate, polycarbonateresin, polyarylate resin, polyacetal resin, polyphenylene sulfide resin,acrylate resin, and so forth can be used. Among these, polyester ispreferable from the perspective of strength, heat resistance, andtransparency. Furthermore, of the polyester resins,polyethylene-2,6-naphthalate and polyethylene terephthalate are morepreferable, and polyethylene terephthalate is particularly preferable.

The above-described resin may be a homopolymer resin, a copolymer, or ablend thereof. Furthermore, various types of additives, for example,antioxidants, antistatic agents, crystal nucleus agents, inorganicparticles, organic particles, viscosity reducing agents, heatstabilizers, lubricants, infrared absorbents, ultraviolet absorbents,and so forth, may be added to the above-described resin.

The term “polyester.” here means polyester resin which is apolycondensation product of a dicarboxylic acid component skeleton and adiol component skeleton, and polyethylene terephthalate, polybutyleneterephthalate, polyethylene-2,6-naphthalate, poly-1,4-cyclohexanedimethylene terephthalate, and the like can be employed, for example. Inparticular, polyethylene terephthalate is preferable, because it excelsin mechanical properties and availability at low prices, andaccordingly, it can be widely employed for various purposes. Theabove-described polyester resin may be a homopolymer resin, a copolymer,or a blend. Examples of dicarboxylic acid components capable ofcopolymerization include isophthalic acid, phthalic acid,1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid,2,6-naphthalene dicarboxylic acid, 4-4′-diphenyl dicarboxylic acid,4,4′-diphenyl sulfone dicarboxylic acid, sebacic acid, dimer acid, andthe like.

Also, examples of glycol components capable of copolymerization include1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol,diethylene glycol, polyalkylene glycol, 2,2-bis(4′-β-hydroxyethoxyphenyl) propane, 1,4-cyclohexane dimethanol, and thelike.

With the glass protecting film according to the first aspect, a layer inwhich polyethylene terephthalate or polyethylene naphthalate is a maincomponent and a layer in which copolymer polyester having1,4-cyclohexane dimethanol as one of the components is a main component,are preferably alternately layered in the thickness direction. Morepreferably, a layer in which polyethylene terephthalate is a maincomponent and a layer in which copolymer polyester having1,4-cyclohexane dimethanol as one of the components is a main component,are preferably alternately layered in the thickness direction. In such astructure, tear resistance, impact resistance, and high transparency canbe effectively and simultaneously achieved.

In the glass protecting film according to the first aspect, haze ispreferably 3% or less, more preferably 2.5% or less, and particularlypreferably 2% or less. When haze is more than 3%, for example, in a casewhere high transparency is required such as a glass protecting film fora display, it may be difficult to recognize an image in detail throughthe film.

The glass transition temperatures of thermoplastic resin which iscomprised the glass protecting film according to the first aspect ispreferably 50° C. or higher in each case, and more preferably 60° C. orhigher. Though an upper limit is not particularly stipulated, an upperlimit of the glass transition temperature of employed as a glassprotecting film is preferable 250° C. or lower, and more preferably 220°C. or lower. When the glass transition temperature of the thermoplasticresin is lower than 50° C., the thermoplastic resin which is used as aglass protecting film may change in dimensional, change in color, orbecome hazy due to heat from the sunlight or a display. When the glasstransition temperature 250° C. or higher, it may causes difficulties infilm formation.

The glass protecting film according to the first aspect cansimultaneously achieve improvement of tear resistance and significantimprovement of impact resistance and also high transparency, which isimpossible with the conventional techniques, by comprising at least onelayer which comprising polyester having 1,4-cyclohexane dimethanol asone of the components. Consequently, applying the glass protecting filmonto glass enables preventing the glass from damage, and also enablesprecisely recognizing an image in detail through the film.

Next, description will be made regarding a glass protecting filmaccording to a second aspect, which comprises a multi-layer structurewhich comprises at least two kinds of thermoplastic resin of which thedifference in glass transition temperature is 40° C. or lower, in whichface-impact strength is 18 J/mm or more, and in which haze is 3% orless.

In the glass protection film according to the second aspect, haze needsto be 3% or less, more preferably 2.5% or less, and most preferably 2%or less. When haze is more than 3% in haze, in a case where hightransparency is required such as a glass protecting film for a display,an image cannot be precisely recognized in detail through the film.Reducing haze can be achieved by, for example, a method for reducingparticles contained in resin, and a method for reducing the primaryparticle diameter of particles to 0.1 μm or less. In particular, thecontent of particles is preferably 0.5% by weight or less, and morepreferably 0.1% by weight or less.

The difference in glass transition temperature between the at least twotypes of thermoplastic resin comprised in the glass protection filmaccording to the second aspect needs to be 40° C. or lower. Thedifference in the glass transition temperature is more preferably 30° C.or lower, and most preferably 25° C. or lower. Suppressing thedifference of the glass temperatures to 40° C. or lower can effectivelyprevent increase of haze and deterioration of impact resistance in theheat treatment process for forming the film.

The glass transition temperatures of thermoplastic resins which iscomprised the glass protection film according to the second aspect areeach preferably 50° C. or higher. When the glass transition temperaturesof thermoplastic resin are lower than 50° C., dimensional change, changein color, or becoming hazy may be caused due to heat from the sunlightor the display when employed as a glass protecting film.

With regard to the phenomenon wherein breakage due to impact breakage offilm are caused, it is considered that effective means for preventingglass from breakage are to improve face-impact-resistance in the initialstage that triggers the breakage, and to improve tear resistance inexpansion of broken portions following the initial stage, so to obtaineffects preventing glass damage and glass scattering, it is necessary tokeep a balance between these two properties.

The glass protection film according to the second aspect needs to haveface-impact strength of 18 J/mm or more. When the face-impact strengthis less than 18 J/mm, the strength required for a glass protecting filmis insufficient to effectively prevent glass from damage and to preventglass fragments from scattering following glass damage.

Face-impact strength is more preferably 20 J/mm, and in particularpreferably 25 J/mm or more. An upper limit of face-impact strength ispreferably 100 J/mm or less, though an upper limit is not especiallystipulated. When face-impact strength is 100 J/mm or less, handlingfurther improves regarding the work of applying the film onto glass, andthereby it is preferable.

Face-impact strength indicates impact absorption energy which ismeasured with a falling-weight-impact testing machine conforming to ASTMD3763. An example of the falling-weight-impact testing machine is agraphic impact tester manufactured by Toyo Seiki Inc.

Moreover, a glass protecting film with face-impact strength of 18 J/mmor more is preferably a glass protecting film having impact strength of8 to 40 J, and more preferably 10 to 40 J. On the other hand, whenimpact strength is 40 J or more, handling sometimes deteriorates in thework of applying the film onto glass.

Impact strength indicates impact absorption energy which is measuredwith a pendulum-type-impact testing machine. An example of thependulum-type-impact-testing machine is a puncture tester manufacturedby Testing Machine Inc. The pendulum-type-impact testing machine employsa method for evaluating impact resistance as to the face of a film aswith a falling-weight-impact testing machine. A hammer portion of thependulum-type-impact testing machine preferably has a cone shape so asto measure a thick sample with film thickness of 50 μm or more, and morepreferably is a triangular pyramid. In the case of the hammer portion ofa triangular pyramid, a glass protecting film with face-impact strengthof 18 J/mm may have impact strength of 8 to 40 J.

Accordingly, the glass protecting film according to the second aspect,comprising a multi-layer structure which comprises at least two types ofthermoplastic resin of which the difference of glass transitiontemperature is 40° C. or lower, in which face-impact strength is 18 J/mmor more, and in which haze is 3% or less, may be a glass protecting filmcomprising a multi-layer structure which comprises at least two types ofthermoplastic resin of which difference of glass transition temperatureis 40° C. or lower, and in which impact strength is 8 to 40 J, and inwhich haze is 3% or less.

Examples of thermoplastic resin employed in the glass film according tothe second aspect include, for example, polyolefine resin such aspolyethylene, polypropylene, polymethylpentene, and the like, polyamideresin such as nylon 6, nylon 66, and the like, polyester resin such aspolyethylene terephthalate, polybutylene terephthalate,polyethylene-2,6-naphthalate, polycarbonate resin, polyarylate resin,polyacetal resin, polyphenylene sulfide resin, acrylate resin, and soforth. Polyester is preferable from the perspective of impactresistance, transparency, and heat stability, and polyester in whichethylene terephthalate or ethylene-2,6-naphthalate is a main componentis more preferable. In particular, polyethylene terephthalate ispreferable, because it has excellent mechanical properties, is availableat low costs, and is applicable to wide-ranging purposes.

The above-described resin may be a homopolymer resin, a copolymer, or ablend. Examples of dicarboxylic acid components capable ofcopolymerization include isophthalic acid, phthalic acid,1,4-naphthalene dicarboxylic acid, 1,5-naphthalene dicarboxylic acid,2,6-naphthalene dicarboxylic acid, 4-4′-diphenyl carboxylic acid,4,4′-diphenyl sulfone dicarboxylic acid, sebacic acid, and dimer acid.Examples of glycol components capable of copolymerization include1,2-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentadiol,diethylene glycol, polyalkylene glycol, 2,2-bis(4′-β-hydroxyethoxyphenyl) propane, 1,4-cyclohexane dimethanol, and thelike.

Furthermore, various types of additives, for example, antioxidants,ultraviolet absorbents, antistatic agents, crystal nucleus agents, fireretardants, inert inorganic particles, organic particles, viscosityreducing agents, heat stabilizers, lubricants, infrared absorbents, andso forth, may be added to the above-described resin as long as theadvantages are not inhibited by the additives. In particular, in theevent of employing functional particles, providing a layer having theabove-described functions onto a film surface layer portion using amethod such as coating or the like is more effective in reducing hazethan a method for dispersing particles in resin.

With the glass protecting film according to the second aspect, themethod for manufacturing thermoplastic resin is not restricted to anyparticular method.

A layer in which polyethylene terephthalate or polyethylene naphthalateis a main component, and a layer in which copolymer polyester having1,4-cyclohexane dimethanol as one of the components is a main component,are preferably alternately layered in the thickness direction. Morepreferably, a layer in which polyethylene terephthalate is a maincomponent, and a layer in which copolymer polyester having1,4-cyclohexane dimethanol as one of the components is a main component,are preferably alternately layered in the thickness direction. In such aconfiguration, tear resistance, impact resistance, and high transparencycan be effectively and simultaneously achieved.

The glass protecting film according to the second aspect preferablycomprises at least one layer which comprises polyester having1,4-cyclohexane dimethanol as one of the components. Improvement of tearresistance, significant improvement of impact resistance, and also hightransparency can be simultaneously achieved by including at least onelayer which comprises polyester having 1,4-cyclohexane dimethanol as oneof the components. Furthermore, applying a glass protecting film ontoglass further improves preventive capabilities for glass damage and alsoenables precisely recognizing an image in detail through the film.

The glass protecting film according to first and second aspectspreferably comprises at least one layer which comprises polyester having2,2-bis (4′-β-hydroxyethoxyphenyl)propanol as one of components.Improvement of tear resistance, significant improvement of impactresistance, and also high transparency can be simultaneously achieved byincluding at least one layer which comprises polyester having 2,2-bis(4′-β-hydroxyethoxyphenyl) propanol as one of components. Furthermore,applying our glass protecting films onto glass further improvespreventive capabilities for glass damage and also enables preciselyrecognizing an image in detail through the film. As for compounds havinga 2,2-bis (4′-β-hydroxyethoxyphenyl) propane structure, a bisphenol Aethylene oxide additive is preferably employed.

With the first and second aspects, polyester having 1,4-cyclohexanedimethanol as one of the components, copolymerization of 1,4-cyclohexanedimethanol is preferably 20 to 50 mol %, though it is not particularlyrestricted. Copolymerization of 1,4-cyclohexane dimethanol is morepreferably 30 to 40 mol %. When copolymerization of 1,4-cyclohexanedimethanol is 20 to 50 mol %, tear resistant effect remarkably improves.

The laminated constitution of the glass protecting film according to thefirst aspect needs to comprise at least 5 or more layers.

Also, the laminated constitution of a glass protecting film according tothe second aspect needs to comprise at least 2 layers.

Furthermore, the laminated constitution of the glass protecting filmaccording to the first and second aspects is preferably 8 to 256 layers,more preferably 16 to 128 layers, and most preferably 32 to 128 layers.Including 8 or more layers in multi-layer laminated constitutionprevents impact from being propagated in the thickness direction,thereby obtaining dramatic glass damage prevention effects.

Also, with the glass protecting film according to the first and secondaspects, the following formula (1) is preferably satisfied.

Film thickness: T (μm)

Total number of layers: L1.2≦T/L≦30   (1)1.5≦T/L≦25 is more preferable, and 1.8≦T/L≦20 is further preferable.When T/L is less than 1.5, propagation of cracking due to impact cannotbe sufficiently prevented, whereby sufficient effects regarding impactresistance and tear resistance cannot be obtained, and thus it is notpreferable.

With the glass protecting film according to the first and secondaspects, the thickness of a layer containing polyester having1,4-cyclohexane dimethanol as one of components is preferably 0.05 to 30μm, more preferably 0.1 to 25 μm, and further preferably 0.2 to 20 μm.When the thickness of a layer which comprises polyester having1,4-cyclohexane dimethanol as one of the components is thinner than 0.05μm, sufficient impact resistant capabilities may not be obtained. On theother hand, when the thickness is 30 μm or more, sufficient tearresistant capabilities may not be obtained.

With the glass protecting film according to the first and secondaspects, the thickness of the film is preferably 10 to 500 μm, morepreferably 20 to 400 μm, and further preferably 50 to 200 μm. When filmthickness is less than 10 μm, it may be difficult to manufacture a filmwith high impact resistance, and on the other hand, when film thicknessis greater than 500 μm, it may be difficult to manufacture a film havinghigh transmittance of visible light, and accordingly, handling sometimesdeteriorates in the work of applying the film onto glass, and thus isnot preferable.

With our glass protecting films, at least one surface layer of a filmformed of thermoplastic resin preferably includes an easy-adhesivelayer, an adhesive layer, an anti-reflective layer, and a hard coatlayer. Various types of conventional known techniques and so forth canbe applied for these layers without being restricted to a particulartechnique. Including these layers in at least one surface layer of afilm which comprises thermoplastic resin is preferable, since it allowsthe film to stick onto glass of a flat display and the like as a glassprotecting film, allows preventing reflection of images on the surfaceof the glass, and also allows preventing cases wherein it is difficultto precisely recognize an image through the film due to scratches.

With the glass protecting film according to the first and secondaspects, pencil hardness on at least one side of a film is preferably 2Hor harder. 3H or more is more preferable, and 4H or more is furtherpreferable. When pencil hardness is less than 2H, it may be difficult toprecisely recognize an image through the film since the surface of thefilm is readily scratched when employed as a glass protecting film.

As for a method for improving pencil hardness on at least one side ofthe film to 2H or more, providing a hard coat layer on at least one sideof the film is preferable. As for the method for improvingabrasion-proofing by improving hardness, a common method whereinhardness is increased can be applied to this case, but a method forpreventing the hard coat layer from cracking by reducing the thicknessof the hard coat layer beyond the normal thickness is preferablyemployed.

Though components forming a hard coat layer are not restricted to anyparticular one, a preferably resin is formed by reaction of amultifunctional (meta)acrylate-containing-compound having at least one(meta)acryloyl group in one molecule. Here, reaction includes theconcept of polymerization, copolymerization, degeneration, and so forth.

Specific examples of multifunctional (meta)acrylate includepentaerythritol tri(meta)acrylate, pentaerythritol tetra(meta)acrylate,dipentaerythritol tri(meta)acrylate, dipentaerythritoltetra(meta)acrylate, dipentaerythritol penta(meta)acrylate,dipentaerythritol hexa(meta)acrylate, trimethylol propanetri(meta)acrylate, n-butyl(meta)acrylate, polyester(meta)acrylate,lauryl(meta)acrylate, hydroxyethyl(meta)acrylate,hydroxypropyl(meta)acrylate, and so forth. With these examples, one ormore types of monomer may be mixed.

Resin making up a hard coat layer may be formed of a combination ofmultifunctional (meta)acrylate alone, or may include other well-knownreaction compounds. Preferably, the resin includes multifunctional(meta)acrylate by 80 mol % or more.

Though the thickness of the hard coat layer is appropriately selectedaccording to usage, this is commonly 0.5 to 30 μm, and preferably 1 to 8μm. When the thickness of a hard coat layer is less than 0.5 μm, surfacehardness is apt to deteriorate, thereby readily suffering scratches. Onthe other hand, when the thickness is more than 30 μm, in some cases,cracking may be propagated over the hard coat layer under impact, andaccordingly impact strength may be apt to deteriorate. In addition, thehardened film may become fragile, and accordingly, cracking may tend tooccur when the film is folded.

With the glass protecting film according to the first and secondaspects, transmittance of near-infrared rays is preferably 20% or less,more preferably 18% or less, and further preferably 16% or less. Whentransmittance of near-infrared rays exceeds 20% and when a film isemployed as a glass protecting film for a plasma display, field emissiondisplay, CRT display, and so forth, near-infrared rays emitted from thedisplay pass through the glass protecting film may cause control ofremote control switches and so forth to behave abnormally.

Though a method for reducing transmittance of near-infrared ray to 20%or less is not restricted to any particular method, this can be achievedby, for example, dispersing a near-infrared absorbent in thethermoplastic resin or the adhesive layer, or providing a near-infraredshielding layer in or on the glass protecting film, or the like.

With the glass protecting film according to the first and secondaspects, transmittance of visible light is preferably 70% or more.Transmittance of visible light is more preferably 80% or more, and mostpreferably 90% or more. When transmittance of visible light is 70% orless, it may be difficult to precisely recognize an image through thefilm, thereby it is not preferable as a glass protecting film for adisplay.

Though the method for increasing transmittance of visible light is notrestricted to any particular method, for example, a method for reducingdifference of refraction indexes between respective thermoplastic resinsforming a multi-boundary structure, a method for reducing dispersiondiameter thereof to 0.1 μm or less in the event that one or morethermoplastic resins are dispersed in an island shape, and so forth, arepreferably employed.

With the glass protecting film according to the first and secondaspects, tensile elongation at break is preferably 100 to 300%. Tensileelongation at break is more preferable 130 to 250%. Moreover, tensilestress at break at that time is preferably 120 to 400 MPa, morepreferably 150 to 250 MPa. When tensile elongation at break is 100 to300% and tensile stress at break is 120 to 400 MPa, explosion-protectioncapabilities of the glass protecting film is excellent, and accordingly,glass breakage and glass fragments scattering following glass breakageis effectively prevented, and thereby it is preferable. Tensileelongation at break of 100 to 300% and tensile stress at break of 120 to400 MPa is also preferable from a viewpoint of handling in working.

With a laminated film according to the first and second aspects,respective polyester resins which are comprised each layer preferablyhave a Young's modulus of 1400 MPa or more, and more preferably 2000 MPaor more. Though an upper limit is not particularly stipulated, a Young'smodulus of polyester resins is preferably 6000 MPa or less. Polyesterhaving a Young's modulus of 1400 MPa or more is not readily transformeddue to outer force, and thereby it is effective for improvingface-impact capacity. When the above-described ranges are satisfied,uneven thickness readily may occur in the stretching process for formingthe film. Moreover, distortion may occur in images viewed through thefilm, and it is not preferable. On the other hand, when a Young'smodulus exceeds 6000 MPa, it may be difficult to perform stretching atthe time of film formation.

With the first and second aspects, tearing-propagation resistance in thelongitudinal and/or width direction is preferably 10 N/mm or more, morepreferably 30 N/mm or more, and further preferably 50 N/mm or more. Whentearing-propagation resistance is less than 10 N/mm, strength may besometimes insufficient for a film as a glass protecting film toeffectively prevent glass breakage and glass fragments scatteringfollowing glass breakage.

The glass protecting film according to the first and second aspects canbe applied onto the front face of glass for a flat display. The term“flat display” denotes a flat CRT display, a liquid crystal display, aplasma display, an organic EL display, a field emission display, or thelike, and in particular, the glass protecting film is suitably employedas a glass protecting film for a flat CRT display or plasma display.

Specific examples regarding a method for manufacturing the glassprotecting film will be described, but the films and methods are notrestricted to these examples.

Thermoplastic resin is arranged in a form of pellets. Pellets aresufficiently dried in heated air or under vacuum if necessary, followingwhich the dried pellet is supplied to a melting extruder which is heatedto a temperature more than the melting point of thermoplastic resinunder a nitrogen airflow or under vacuum so as not to deteriorate theintrinsic viscosity, extruded from a die, and cooled over a casting drumwith a temperature less than the glass transition point of thermoplasticresin, so as to form an undrawn film. At this time, rapid coolingsolidification is preferably performed by contact with a cooling membersuch as a casting drum and so forth employing electrodes in a wireshape, tape shape, needle shape, knife shape, or the like, usingelectrostatic force. Moreover, employing various types of filters foreliminating foreign particles, denatured polymer within the meltingextruder, for example, a filter formed of material such as sinteredmetal, porous ceramic, sand, wire mesh, and so forth, is preferable forreduction of haze. Filtration precision of a filter is preferablyselected based on the particle diameter of inert particles to beemployed, and in particular, it is important to employ a filter withfiltration precision capable of eliminating foreign particles anddenatured polymer with a particle diameter of 20 μm, preferably a filterformed of wire mesh, in order to reduce haze to 3% or less, preferably2.5% or less.

Furthermore, following passing through various types of filters, makingthe extrusion amount uniform by employing a gear pump and the like inthe polymer flow path is preferably for reducing layered unevenness ofeach layer.

An example of a method for obtaining a multi-layer film is a method forlayering thermoplastic resin extruded from different flow pathsemploying two or more extruders in a multi-layer structure employing amulti-manifold die, feed block, static mixer, or the like. Furthermore,these may be optionally combined.

Next, this undrawn film may be stretched in the longitudinal of the filmand/or in the width direction. As for a stretching method, a successivebiaxial stretching method for successively stretching the undrawn filmin the longitudinal direction and in the width direction employing rollsand stenter may be used. Moreover, a simultaneous biaxial stretchingmethod for simultaneously performing longitudinal drawing and lateralstretching of the undrawn film employing a stenter has shorter a processthan that in a successive biaxial stretching method, leading to costreduction, and further, stretching breakages and roll scuffs hardlyoccur, and thereby is particularly effective in the glass protectingfilm. Furthermore, a stretching-again-longitudinally method forstretching the film, successively stretched in the lateral andlongitudinal directions, in the longitudinal direction again isparticularly effective for strengthening the film in the longitudinaldirection. Following the above-described method for stretching againlongitudinally, a method for stretching again longitudinally andlaterally, for stretching the film in the lateral direction again, isextremely effective in the event of further strengthening the film inthe lateral direction. A longitudinal-multi-stage-stretching method forstretching a film in two or more steps in the longitudinal direction,and stretching the film in the lateral direction, is particularlyeffective.

In the event of employing a successive biaxial stretching method, forexample, though stretching conditions in the longitudinal direction varydepending on the thermoplastic resin employed, 2 to 15 times is commonlypreferable, 2.5 to 10 times is preferable in a case of employingpolyester resin, and 3.0 to 5 times is further preferable. Moreover, thestretching speed is preferably 1000 to 50000%/minute, and the stretchingtemperature is preferably the glass transition temperature of Tg of thethermoplastic resin having the highest component ratio or higher, and(glass transition temperature +50° C.) or lower, thereby obtaining auniaxial orientation film by stretching the film in the longitudinaldirection.

An easy-adhesive layer, easy-sliding layer, or high light-raytransmittance may be provided on the surface of the drawn film thusobtained by being subjected to coating employing a well-known coatingtechnique such as gravure coater or metalling bar. These coatings may bedispensed off-line following biaxial stretching, or in-line by beingintroduced between the longitudinal stretching process and lateralstretching process. In particular, in the event of employing functionalparticles, a technique for performing application on the surface of afilm employing a technique such as coating and so forth is moreeffective than a technique for dispersing particles in the resin, toimprove transmittance of all light rays and reduce haze values.

With stretching in the width direction, employing a tenter which hasbeen conventionally employed, the stretching temperature is preferablythe glass transition temperature of Tg of thermoplastic resin having thehighest component ratio or higher, and (glass transition temperature Tg+80° C.) or lower, more preferably the glass transition temperature ofTg or higher but (glass transition temperature Tg +40° C.) or lower, andthe stretching is preferably 2.0 to 10 times, more preferably 2.5 to 5times. At that time, the stretching speed is not especially restricted,but 1000 to 50000%/minute is preferable.

Furthermore, a biaxial orientation film may be subjected to stretchingin at least one direction of longitudinal direction and width directionagain if necessary. In this case, with longitudinal stretching which isperformed again, the stretching temperature is preferably (glasstransition temperature of Tg +20° C.) of thermoplastic resin having thehighest component ratio or higher, and (glass transition temperature+120° C.) or lower, more preferably (glass transition temperature of Tg+50° C.) or higher but (glass transition temperature +100° C.) or lower,and stretching is preferably 1.2 to 2.5 times, more preferably 1.2 to1.7 times. Moreover, with lateral stretching which is performedfollowing longitudinal stretching, the stretching temperature ispreferably (glass transition temperature of Tg +20° C.) of thermoplasticresin having the highest component ratio or higher but (glass transitiontemperature +150° C.) or less, more preferably (glass transitiontemperature of Tg +50° C.) or higher but (glass transition temperature+130° C.) or lower, and stretching is preferably 1.02 to 2 times, morepreferably 1.1 to 1.5 times.

Alternately, in the event of drawing with a simultaneous biaxialstretching method, a simultaneous biaxial stretching method with atenter which employs a linear motor driving method is preferablyemployed. With a stretching temperature of a simultaneous biaxialstretching method, the glass transition temperature of Tg ofthermoplastic resin having the highest component ratio or higher but(glass transition temperature tg +50° C.) or lower is preferable. In theevent of the stretching temperature drastically deviates from thisrange, uniform drawing cannot be performed, and uneven thickness andfilm breaks sometimes occurs, which is undesirable. Stretchingmagnification is preferably 3 to 10 times in each of the longitudinaland lateral directions. The stretching speed is not particularlyrestricted, but 2000 to 50000%/minute is preferable.

Next, to reduce heat shrinkage and provide planarity to a film, heattreatment is performed if necessary.

To obtain high mechanical properties wherein extension of fracture is100 to 300% in at least one direction of the longitudinal and widthdirections, and stress of fracture is 120 to 400 MPa therein, and toobtain thermal dimensional stability, preferable heat treatmentconditions are to perform heat treatment in a range between the glasstransition temperature of Tg of thermoplastic resin having the highestcomponent ratio and (glass transition temperature +100° C.), either atits natural length, slightly stretched, or in a slacked state, for 0.5to 60 seconds.

To obtain low haze, most preferred treatment conditions includeperforming heat treatment in a range between (glass transitiontemperature tg +40° C.) of thermoplastic resin having the highestcomponent ratio and (glass transition temperature +80° C.) for 0.5 to 10seconds. In the event that the stretching temperature is lower than(glass transition temperature tg +40° C.) of thermoplastic resin havingthe highest component ratio, heat shrinkage may become large, on theother hand, in the event that the stretching temperature is higher than(glass transition temperature +80° C.) of the thermoplastic resin havingthe highest component ratio, haze increases, and impact resistance maydeteriorate.

With a glass protecting film in which transmittance of visible light is70% or more, preferably 80% or more, more preferably 90% or more,anti-reflective layer is preferably on one surface layer of the film.Anti-reflective layer is not particularly restricted to any one, soconventionally well-known techniques may be used.

The biaxial orientated film which has been heat-treated as occasiondemands is slowly cooled down to a room temperature and rewound with awinder. A slow cooling method is preferable for slowly cooling the filmdown to a room temperature in two or more divided steps. At this time,performing relaxation of 0.5 to 10% around in the longitudinal and widthdirections is effective for reducing thermal dimensional stability. Asfor a cooling temperature, a first step is preferably a range between(heat treatment temperature −80° C.) and (heat treatment temperature−20° C.), and a second step is preferably a range between (thetemperature of the first step −40° C.) and (the temperature of the firststep −30° C.), but not restricted to this.

Evaluation methods for physical properties will be described.

Evaluation Methods for Physical Properties:

(1) Tear Strength and Tearing-propagation Resistance

Tear strength was measured with a heavy-loading-tear testing machinemanufactured by Toyo Seiki Inc. Samples 60 mm wide and 70 mm long insize were slit up on a central portion in the width direction from theend thereof by 20 mm, and the remained 50 mm was torn, and an indicatingvalue was read out. Also, multiplying this indicating value (g) by 9.8provided tear strength (mN). Note that this tearing strength was a meanobtained from the test results of respective 5 samples in thelongitudinal direction and in the lateral direction. Also, tearingstrength per film thickness of 1 mm was obtained as tearing-propagationresistance (N/mm).

(2) Transmittance of all Light Rays and Haze

Measurement was performed with a direct-reading hazemeter manufacturedby Suga Test Instruments Co. Ltd. Haze values (%) were obtained fromdividing diffusion transmittance by transmittance of all light rays, andmultiplied by 100.

(3) Falling-Ball Impact-Absorption Energy

Measurement was performed with a falling-ball testing machinemanufactured by DAIEI KAGAKU SEIKI MFG CO. LTD. Measurement wasperformed in a situation wherein a metal sphere (weight: 1.809 kg)disposed at 2.5 m height above a test film which was fixed in a framewas dropped, and measured values were obtained from the passing of timebetween two points of upper and lower portions of the test film in theevent of breaking the test film. Note that lubricant “Three Bond 1804”was blown onto the surface of the test film by spraying. Note that thefalling-ball impact-absorption energy E(J) was obtained from thefollowing expression, and a mean of 5 samples was adopted.E=1.809×(1/t₀ ²−1/t ₁ ²)/200

t₀: passing time without test films (ms)

t₁: passing time with test films (ms)

(4) Glass Scattering Prevention Test

Measurement was performed conforming to JIS A5759-1998 A method. Arating of a double circle was given in the event that glass was notbroken, a circle in the event that glass was broken without scattering,and a cross in the event that glass was broken with scattering. Ofthese, the items with the double circle or the circle rating passed thistest.

(5) Near-infrared Ray Transmittance

Measurement was performed with a spectrophotometer MPC-3100.Transmittance of all light rays on a range between wavelength of 800 nmand wavelength of 2100 nm was measured, and the average light raytransmittance in a near-infrared region between 800 nm and 1200 nm wastaken as near-infrared ray transmittance.

(6) Pencil Hardness

Measurement was performed conforming to JIS-K5400. Measurement wasperformed in a situation wherein pencils with various hardness werepressed against a film layer at an angle of 90°, and the pencil hardnessis the hardness of the pencil at the time of a scratch occurring whenscratching under a weight of 1 kg.

(7) Intrinsic Viscosity

Measurement was performed at a temperature of 25° C. employingorthochlorophenol as a solvent.

(8) Layer Structure and Layer Thickness

The layer structure of the film was obtained by cross-sectionobservation. That is to say, measurement was performed in a situationwherein a cross-section of a film was enlarged 3000 to 200000 times andobserved employing a HU-12 model transmission electron microscopemanufactured by Hitachi, Ltd., then cross-sectional photographs weretaken, and layer structure and each layer thickness was measured.

(9) Impact Strength

Measurement was performed employing a pendulum-type-impact testingmachine manufactured by Testing Machines Inc. Measurement was performedin a situation wherein in the event that a film fixed to a frame wassubjected to impact in the vertical direction employing a hammer in atriangular pyramid, difference of positional energy between a hammeruplifted position and downstroke position was read out by an indicatingneedle when breakage was detected, and this impact absorption energy wastaken as impact strength (J). The shape of the hammer was a triangularpyramid, 62 mm on each side one the bottom, and a height of 25 mm, whichwas attached with a weight of 10 kg. The height from an impact point ofthe sample film to the hammer uplifted position was 300 mm. Note thatwith the test, 10 samples were measured while changing the orientationof the film to be adhered to a frame at an angle of 90° at a time, and amean value thereof was obtained.

(10) Glass Transition Temperature

Measurement was performed employing a DSC RDC220 manufactured by SeikoInstruments Inc. as a differential scanning calorimeter, and a diskstation SSC/5200 also manufactured by the same company as a dataanalyzer. The measurement of a glass transition temperature Tg (° C.)was performed in a situation wherein a sample of approximately 5 mg wasenclosed in an aluminum pan, held at 300° C. for 5 minutes, subjected torapid cooling with liquid nitrogen, and then measured at programmingrate of 20° C./minute.

(11) Tensile Stress at Break and Tensile Elongation at Break

Measurement was performed conforming to the following method stipulatedin ASTM-D882 and employing an instron-type tensile tester (“TensilonAMF/RTA-100” tensile strength automatic tester, manufactured byOrientec). A 10 mm wide sample film was stretched under the conditionsof a testing distance of 100 mm and a pulling speed of 200 mm/minute.Tensile stress at break and tensile elongation at break were obtainedfrom the yield fracture point of a tension-strain curve. The measurementwas performed in an atmosphere of 25° C. and 65%/RH.

(12) Face Impact Strength

Measurement was performed conforming to ASTM D 3763 and employing agraphic impact tester manufactured by Toyo Seiki Inc. Full impactabsorption energy (J) at the time of the cone passing through the filmwas converted into increments of thickness (1 mm), thereby obtaining theface impact strength (J/mm).

(13) Young's Modulus

Young's modulus of thermoplastic resin which was comprised each layerwas measured conforming to ASTM test method D882-88. An undrawn film wasemployed as a sample film, which was obtained by being subjected torapid cooling solidification on a casting drum controlled at atemperature of 25° C. so as to improve contact of the drum and film witha known electrostatic applying device. The measurement was performedemploying an instron-type tensile tester (“Tensilon AMF/RTA-100”.tensile strength automatic tester, manufactured by Orientec). A 10 mmwide sample film was stretched under the conditions of a testingdistance of 100 mm and a pulling speed of 200 mm/minute so as to obtainthe Young's modulus.

(14) Hardened-Glass Falling-Ball Test

To study resistance as to impact strength stronger than a glassscattering prevention test, a hardened-glass falling-ball test wasperformed conforming to the JIS R3206 falling-ball test. The test wasperformed in a situation wherein a film was applied onto one face ofglass, and a rigid sphere was dropped on the other face of the glass towhich the film was not applied. This test was performed for 2 specimens,as a result, in the event that the rigid sphere passed through all 2specimens, this was rated with a cross, and in the event that the rigidsphere did not pass through at least 1 specimen, this was rated with acircle, and accordingly, those rated with a circuit indicated passingthis test. For the glass, 5-mm-thick float glass was employed. As forthe rigid sphere, a sphere with a diameter of 82 mm and weight of 2260 gwas employed. The falling height of the rigid sphere was 3.0 m.

We now refer to representative examples.

EXAMPLE 1

Polyethylene terephthalate (glass transition temperature of 81° C.,Young's modulus of 1990 MPa) having intrinsic viscosity of 0.8 wasemployed as a thermoplastic resin A. Copolymer polyester (EasterPETG9921 manufactured by Eastman Chemical Company) (glass transitiontemperature of 82° C., Young's modulus of 2200 MPa) in whichterephthalic acid as dicarboxylic acid components, 1,4-cyclohexanedimethanol of 10 mol % and ethylene glycol of 90 mol % as diolcomponents were copolymerized, was employed as a thermoplastic resin B.The thermoplastic resins A and B were each dried, and then supplied toan extruder.

The thermoplastic resin A and B were each in a molten state of 280° C.at the extruder, and combined at a field block following passing througha gear pump and filter. The combined thermoplastic resin A and B weresupplied to a static mixer, and a structure formed of 65 layers of thethermoplastic resin A and 64 layers of the thermoplastic resin B formedof 64 layers, alternately layered in the thickness direction, wasformed. Here, adjustment was made with the discharge rate such thatratio of laminated thickness was A/B=5. A laminated member made up ofthe thus-obtained 129 layers in total was supplied to a T-die and moldedin a sheet shape, and then was subjected to rapid cooling solidificationon a casting drum held at a surface temperature of 25° C., while beingsubjected to electrostatic application.

The obtained cast film was heated at a roll group set at 90° C.,stretched 3.2 times in the longitudinal direction, introduced to atenter, preheated in hot air of 100° C., and then stretched by 3.3 timesin the lateral direction. The drawn film, was subjected without anychange to heat treatment in hot air of 150° C. within the tenter, slowlycooled down to a room temperature, and then rolled up. The obtained filmthickness was 188 μm. The obtained results are shown in Table 1.

EXAMPLE 2

A laminated film was formed of 33 layers of the thermoplastic resin Aand 32 layers of the thermoplastic resin B, the discharge rate of theresin was adjusted such that film thickness was 188 μm, and a drawn filmmade up of 65 layers in total was obtained with the same equipment andconditions as with Example 1. The impact strength of the obtained filmwas 14 J. The obtained results are shown in Table 1.

EXAMPLE 3

For a layering device, a 33 layer laminated field block alone wasemployed, and a laminated film was formed of 17 layers of thermoplasticresin A and 16 layers of the thermoplastic resin B, the discharge rateof the resin was adjusted such that the film thickness was 188 μm, adrawn film made up of 33 layers in total was obtained with the sameequipment and conditions as with Example 1. The obtained results areshown in Table 1.

EXAMPLE 4

For a layering device, a 17 layer laminated field block alone wasemployed, and a laminated film was formed of 9 layers of thethermoplastic resin A and 8 layers of the thermoplastic resin B, thedischarge rate of the resin was adjusted such that the film thicknesswas 188 μm, and a drawn film made up of 17 layers in total was obtainedwith the same equipment and conditions as with Example 1. The impactstrength of the obtained film was 14 J. The obtained results are shownin Table 1.

EXAMPLE 5

For a layering device, an 8 layer multi-manifold die alone was employed,and a laminated film was formed of 4 layers of the thermoplastic resin Aand 3 layers of the thermoplastic resin B, the discharge rate of theresin was adjusted such that the film thickness was 188 μm, and a drawnfilm made up of 7 layers in total was obtained with the same equipmentand conditions as with Example 1. The obtained results are shown inTable 1.

EXAMPLE 6

The laminated thickness ratio A/B between the thermoplastic resin A andthe thermoplastic resin B was 2, the discharge rate of the resin wasadjusted such that the film thickness was 188 μm, and a drawn film madeup of 65 layers in total was obtained with the same equipment andconditions as with Example 2. The obtained results are shown in Table 1.

EXAMPLE 7

The laminated thickness ratio A/B between the thermoplastic resin A andthe thermoplastic resin B was 10, the discharge rate of the resin wasadjusted such that the film thickness was 188 μm, and a drawn film madeup of 65 layers in total was obtained with the same equipment andconditions as with Example 2. The obtained results are shown in Table 1.

TABLE 1 EXAMPLE EXAMPLE EXAMPLE EXAMPLE UNIT 1 2 3 4 COMPONENTS THERMO-NAME OF — PET PET PET PET PLASTIC RESIN RESIN A INTRINSIC — 0.8 0.8 0.80.8 VISCOSITY Tg ° C. 81 81 81 81 THERMO- NAME OF — PETG PETG PETG PETGPLASTIC RESIN 9921 9921 9921 9921 RESIN B Tg ° C. 82 82 82 82 SURFACELAYER — — — — — LAYERING NO. OF LAYERS — 129 65 33 17 LAYERING RATIO A/B— 5 5 5 5 FILM THICKNESS μm 188 188 188 188 FILM STRETCHING MD TIMES 3.23.2 3.2 3.2 FORMATION TD TIMES 3.3 3.3 3.3 3.3 HEAT TREATMENT ° C. 150150 150 150 TEMPERATURE PHYSICAL TRANSMITTANCE OF % 92 92 92 92PROPERTIES ALL LIGHT RAYS OF FILM HAZE % 2 2 2 2 TEAR STRENGTH mN 916010020 9500 8439 FALLING-BALL IMPACT J NO NO NO NO ABSORPTION ENERGYFRACTURES FRACTURES FRACTURES FRACTURES GLASS SCATTERING — ∘ ⊚ ⊚ ⊚PREVENTION TEST EXAMPLE EXAMPLE EXAMPLE 5 6 7 COMPONENTS THERMO- NAME OFPET PET PET PLASTIC RESIN RESIN A INTRINSIC 0.8 0.8 0.8 VISCOSITY Tg 8181 81 THERMO- NAME OF PETG PETG PETG PLASTIC RESIN 9921 9921 9921 RESINB Tg 82 82 82 SURFACE LAYER — — — LAYERING NO. OF LAYERS 7 65 65LAYERING RATIO A/B 5 2 10 FILM THICKNESS 188 188 188 FILM STRETCHING MD3.2 3.2 3.2 FORMATION TD 3.3 3.3 3.3 HEAT TREATMENT 150 150 150TEMPERATURE PHYSICAL TRANSMITTANCE OF 92 92 92 PROPERTIES ALL LIGHT RAYSOF FILM HAZE 2 2 2 TEAR STRENGTH 5300 7366 8199 FALLING-BALL IMPACT NONO NO ABSORPTION ENERGY FRACTURES FRACTURES FRACTURES GLASS SCATTERING ⊚⊚ ◯ PREVENTION TEST Tg: GLASS TRANSITION TEMPERATURE MD: LONGITUDINALDIRECTION OF FILM TD: WIDTH DIRECTION OF FILM

EXAMPLE 8

Polyethylene terephthalate (glass transition temperature of 81° C.,Young's modulus of 1990 MPa) having intrinsic viscosity of 0.65 wasemployed as the thermoplastic resin A, and a drawn film made up of 65layers in total was obtained with the same equipment and conditions aswith Example 2. The obtained results are shown in Table 2.

EXAMPLE 9

Copolymerized polyester (Easter PETG6763 manufactured by EastmanChemical Company) (glass transition temperature of 81° C., Young'smodulus of 1700 MPa) in which terephthalic acid as the dicarboxylic acidcomponent, and 30 mol % 1,4-cyclohexane dimethanol and 70 mol % ethyleneglycol as the diol component were copolymerized, was employed as thethermoplastic resin B, and a drawn film made up of 65 layers in totalwas obtained with the same equipment and conditions as with Example 2.The obtained results are shown in Table 2.

EXAMPLE 10

Polycyclohexane dimethalate (hereafter, referred to as “PCT”) (glasstransition temperature of 95° C., Young's modulus of 1750 MPa) in whichterephthalic acid as the dicarboxylic acid component, and 100 mol %1,4-cyclohexane dimethanol as the diol component were polymerized, wasemployed as the thermoplastic resin B, and a drawn film made up of 65layers in total was obtained with the same equipment and conditions aswith Example 2. The obtained results are shown in Table 2.

EXAMPLE 11

Copolymer polyester (Duraster DS2010 manufactured by Eastman ChemicalCompany) (glass transition temperature of 89° C., Young's modulus of1750 MPa) in which 1,4-cyclohexane dimethanol and isophthalic acid werecopolymerized, was employed as the thermoplastic resin B, and a drawnfilm made up of 65 layers in total was obtained with the same equipmentand conditions as with Example 2. The obtained results are shown inTable 2.

EXAMPLE 12

The discharge rate of the resin was adjusted such that the filmthickness was 150 μm, and a drawn film made up of 65 layers in total wasobtained with the same equipment and conditions as with Example 2. Theimpact strength of the obtained film was 14 J. The obtained results areshown in Table 2.

EXAMPLE 13

The discharge rate of the resin was adjusted such that the filmthickness was 120 μm, and a drawn film made up of 65 layers in total wasobtained with the same equipment and conditions as with Example 2. Theobtained results are shown in Table 2.

EXAMPLE 14

The discharge rate of the resin was adjusted such that the filmthickness was 100 μm, and a drawn film made up of 65 layers in total wasobtained with the same equipment and conditions as with Example 2. Theimpact strength of the obtained film was 9 J. The obtained results areshown in Table 2.

TABLE 2 EXAMPLE EXAMPLE EXAMPLE EXAMPLE UNIT 8 9 10 11 COMPONENTSTHERMO- NAME OF — PET PET PET PET PLASTIC RESIN RESIN A INTRINSIC — 0.650.8 0.8 0.8 VISCOSITY Tg ° C. 81 81 81 81 THERMO- NAME OF — PETG PETGPCT DS2010 PLASTIC RESIN 9921 6763 RESIN B Tg ° C. 82 81 95 89 SURFACELAYER — — — — — LAYERING No. OF LAYERS — 65 65 65 65 LAYERING RATIO A/B— 5 5 5 5 FILM THICKNESS μm 188 188 188 188 FILM STRETCHING MD TIMES 3.23.2 3.2 3.2 FORMATION TD TIMES 3.3 3.3 3.3 3.3 HEAT TREATMENT ° C. 150150 150 150 TEMPERATURE PHYSICAL TRANSMITTANCE OF % 92 92 92 92PROPERTIES ALL LIGHT RAYS OF FILM HAZE % 2 2 2 2 TEAR STRENGTH mN 1001012030 11937 10447 FALLING-BALL IMPACT J NO NO NO NO ABSORPTION ENERGYFRACTURES FRACTURES FRACTURES FRACTURES GLASS SCATTERING — ⊚ ⊚ ⊚ ⊚PREVENTION TEST EXAMPLE EXAMPLE EXAMPLE 12 13 14 COMPONENTS THERMO- NAMEOF PET PET PET PLASTIC RESIN RESIN A INTRINSIC 0.8 0.8 0.8 VISCOSITY Tg81 81 81 THERMO- NAME OF PETG PETG PETG PLASTIC RESIN 9921 9921 9921RESIN B Tg 82 82 82 SURFACE LAYER — — — LAYERING No. OF LAYERS 65 65 65LAYERING RATIO A/B 5 5 5 FILM THICKNESS 150 120 100 FILM STRETCHING MD3.2 3.2 3.2 FORMATION TD 3.3 3.3 3.3 HEAT TREATMENT 150 150 150TEMPERATURE PHYSICAL TRANSMITTANCE OF 92 92 92 PROPERTIES ALL LIGHT RAYSOF FILM HAZE 2 2 2 TEAR STRENGTH 8160 6700 5341 FALLING-BALL IMPACT NONO NO ABSORPTION ENERGY FRACTURES FRACTURES FRACTURES GLASS SCATTERING ⊚◯ ◯ PREVENTION TEST Tg: GLASS TRANSITION TEMPERATURE MD: LONGITUDINALDIRECTION OF FILM TD: WIDTH DIRECTION OF FILM

EXAMPLE 15

The heat treatment temperature was set to 220° C., and a drawn film madeup of 65 layers in total was obtained with the same equipment andconditions as with Example 2. The obtained results are shown in Table 3.

EXAMPLE 16

Polyethylene terephthalate (glass transition temperature of 81° C.)having intrinsic viscosity of 0.8, to which an infrared absorbent of 1%by weight was added, was employed as the thermoplastic resin A, and adrawn film made up of 65 layers in total was obtained with the sameequipment and conditions as with Example 2. The obtained results areshown in Table 3. Note that transmittance of near-infrared rays was 16%.

EXAMPLE 17

An easy-adhesive coating layer made up of silica particles of particlediameter of 30 nm and polyester resin was provided on one face of thefilm, and a drawn film made up of 65 layers in total was obtained withthe same equipment and conditions as with Example 2. The obtainedresults are shown in Table 3.

EXAMPLE 18

An easy-adhesive coating layer made up of silica particles of particlediameter of 30 nm and polyester/polyurethane resin was provided on oneface of the film, and a drawn film made up of 65 layers in total wasobtained with the same equipment and conditions as with Example 2. Theobtained results are shown in Table 3.

EXAMPLE 19

An easy-adhesive coating layer made up of silica particles of particlediameter of 30 nm and acrylic resin was provided on one face of thefilm, and a drawn film made up of 65 layers in total was obtained withthe same equipment and conditions as with Example 2. The obtainedresults are shown in Table 3.

EXAMPLE 20

An anti-reflective layer and a hard coat layer having pencil hardness of4 H were provided on one face of the drawn film made up of 65 layers intotal according to Example 17 and an adhesive layer was provided on theother face. The obtained results are shown in Table 3.

TABLE 3 EXAMPLE EXAMPLE EXAMPLE UNIT 15 16 17 COMPONENTS THERMO- NAME OF— PET PET + PET PLASTIC RESIN INFRARED RESIN A ABSORBENT INTRINSIC — 0.80.8 0.8 VISCOSITY Tg ° C. 81 81 81 THERMO- NAME OF — PETG PETG PETGPLASTIC RESIN 9921 9921 9921 RESIN B Tg ° C. 82 82 82 SURFACE LAYER — —— EASY- ADHESIVE LAYER LAYERING No. OF LAYERS — 65 65 65 LAYERING RATIOA/B — 5 5 5 FILM THICKNESS μm 188 188 188 FILM STRETCHING MD TIMES 3.23.2 3.2 FORMATION TD TIMES 3.3 3.3 3.3 HEAT TREATMENT ° C. 220 150 150TEMPERATURE PHYSICAL TRANSMITTANCE OF % 92 90 90 PROPERTIES ALL LIGHTRAYS OF FILM HAZE % 2 3 4 TEAR STRENGTH mN 6861 10010 10021 FALLING-BALLIMPACT J NO NO NO ABSORPTION ENERGY FRACTURES FRACTURES FRACTURES GLASSSCATTERING — ⊚ ⊚ ⊚ PREVENTION TEST EXAMPLE EXAMPLE EXAMPLE 18 19 20COMPONENTS THERMO- NAME OF PET PET PET PLASTIC RESIN RESIN A INTRINSIC0.8 0.8 0.8 VISCOSITY Tg 81 81 81 THERMO- NAME OF PETG PETG PETG PLASTICRESIN 9921 9921 9921 RESIN B Tg 82 82 82 SURFACE LAYER EASY- EASY- EASY-ADHESIVE ADHESIVE ADHESIVE LAYER LAYER LAYER, ANTI- REFRECTIVE LAYER,HARD COAT LAYER, ADHESIVE LAYER LAYERING No. OF LAYERS 65 65 65 LAYERINGRATIO A/B 5 5 5 FILM THICKNESS 188 188 188 FILM STRETCHING MD 3.2 3.23.2 FORMATION TD 3.3 3.3 3.3 HEAT TREATMENT 150 150 150 TEMPERATUREPHYSICAL TRANSMITTANCE OF 90 92 88 PROPERTIES ALL LIGHT RAYS OF FILMHAZE 4 2 4 TEAR STRENGTH 10029 10015 11097 FALLING-BALL IMPACT NO NO NOABSORPTION ENERGY FRACTURES FRACTURES FRACTURES GLASS SCATTERING ⊚ ⊚ ⊚PREVENTION TEST Tg: GLASS TRANSITION TEMPERATURE MD: LONGITUDINALDIRECTION OF FILM TD: WIDTH DIRECTION OF FILM

COMPARATIVE EXAMPLE 1

The following single-layer film was obtained with the same equipment andconditions as with Example 1. That is to say, only one extruder wasemployed, a feed block and static mixer were not employed, polyethyleneterephthalate having intrinsic viscosity of 0.8 was employed asthermoplastic resin, whereby a single-layer film was obtained. Theobtained film thickness was 188 μm. The obtained results are shown inTable 4.

COMPARATIVE EXAMPLE 2

The following single-layer film was obtained with the same equipment andconditions as with Example 1. That is to say, only one extruder wasemployed, a feed block and static mixer were not employed, copolymerpolyester (PETG9921 manufactured by Eastman Chemical Company) in whichterephthalic acid as the dicarboxylic acid component, and 10 mol %1,4-cyclohexane dimethanol and 90 mol % ethylene glycol as diolcomponents were copolymerized, was employed as thermoplastic resin,whereby a single-layer film was obtained. The obtained film thicknesswas 188 μm. The obtained results are shown in Table 4.

TABLE 4 COMPARATIVE COMPARATIVE UNIT EXAMPLE 1 EXAMPLE 2 COMPONENTSTHERMO- NAME OF — PET PETG PLASTIC RESIN 9921 RESIN A INTRINSIC — 0.80.8 VISCOSITY Tg ° C. 81 82 THERMO- NAME OF — — — PLASTIC RESIN RESIN BTg ° C. — — SURFACE LAYER — — — LAYERING NO. OF LAYERS — — — LAYERINGRATIO A/B — — — FILM THICKNESS μm 188 188 FILM STRETCHING MD TIMES 3.23.2 FORMATION TD TIMES 3.3 3.3 HEAT TREATMENT ° C. 150 150 TEMPERATUREPHYSICAL TRANSMITTANCE OF % 92 90 PROPERTIES ALL LIGHT RAYS OF FILM HAZE% 2 2 TEAR STRENGTH mN 1764 1501 FALLING-BALL IMPACT J 57 70 ABSORPTIONENERGY (FRACTURES) (FRACTURES) GLASS SCATTERING — X X PREVENTION TESTTg: GLASS TRANSITION TEMPERATURE MD: LONGITUDINAL DIRECTION OF FILM TD:WIDTH DIRECTION OF FILM

EXAMPLE 21

A drawn film made up of 7 layers in total was obtained with the sameequipment and conditions as with Example 12 except that 7 layermulti-manifold die alone was employed as a layering device, and alaminated film was formed of 4 layers of the thermoplastic resin A and 3layers of the thermoplastic resin B. However, the discharge rate of theresin was adjusted such that the film thickness was 150 μm. The resultsof the glass scattering prevention test for the obtained film weresatisfactory. The obtained results are shown in Table 5.

EXAMPLE 22

Copolymer polyester (PETG6763 manufactured by Eastman Chemical Company)in which terephthalic acid as the dicarboxylic acid component, and 30mol % 1,4-cyclohexane dimethanol and 70 mol % ethylene glycol as diolthe component were copolymerized, was employed as the thermoplasticresin B.

Both sides of the uniaxial drawn film obtained with the same equipmentand conditions as with Example 3 were subjected to corona dischargetreatment in the atmosphere, wet tension of a base film was set to 55mN/m, the processing face thereof was applied with a coating fluid forforming film layers made up of polyester/melamine cross-linkingagent/silica particles with a mean particle diameter of 140 nm. Theapplied uniaxial drawn film was introduced to a tenter, preheated in hotair of 100° C., and then stretched by 3.3 times in the lateraldirection. The drawn film was subjected to heat treatment in hot air of150° C. within the tenter, slowly cooled down to room temperature, andthen rolled up. The obtained film thickness was 150 μm. The results ofthe glass scattering prevention test for the obtained film weresatisfactory. The evaluation results of the obtained film are shown inTable 5.

EXAMPLE 23

A drawn film was obtained as with Example 22 except that the dischargerate of the resin was adjusted such that the film thickness was 100 μm.The results of the glass scattering prevention test for the obtainedfilm were satisfactory, and the hardened-glass falling-ball test wasalso satisfactory since the rigid sphere did not pass through theobtained glass. The obtained results are shown in Table 5.

EXAMPLE 24

A drawn film was obtained as with Example 22 except that the dischargerate of the resin was adjusted such that the film thickness was 100 μm,and the heat treatment temperature was set to 230° C. The results of theglass scattering prevention test for the obtained film weresatisfactory. The obtained results are shown in Table 5.

EXAMPLE 25

A drawn film was obtained as with Example 22 except that the dischargerate of the resin was adjusted such that the film thickness was 100 μm,an anti-reflective layer and a hard coat layer having pencil hardness of4 H were provided on one face of the obtained film, and an adhesivelayer was provided on the other face of the obtained film. The resultsof the glass scattering prevention test for the obtained film weresatisfactory. The obtained results are shown in Table 5.

EXAMPLE 26

A drawn film made up of 33 layers in total was obtained with the sameequipment and conditions as with Example 22 except that the dischargerate of the resin was adjusted such that the film thickness was 100 μm,and copolymer polyester (hereafter, referred to as “PE·BPA-EO/T (10 mol%)”) (glass transition temperature of 78° C., Young's modulus of 1900MPa) in which terephthalic acid as the dicarboxylic acid component, 90mol % ethylene glycol and 10 mol % bisphenol A ethylene oxide additiveas the diol component were copolymerized, was employed as thethermoplastic resin B. The results of the glass scattering preventiontest for the obtained film were satisfactory. The obtained results areshown in Table 5.

EXAMPLE 27

A drawn film made up of 33 layers in total was obtained with the sameequipment and conditions as with Example 22 except that the dischargerate of the resin was adjusted such that the film thickness was 100 μm,and copolymer polyester (hereafter, referred to as “PE·BPA-EO/T (20 mol%)”) (glass transition temperature of 78° C., Young's modulus of 1900MPa) in which terephthalic acid as the dicarboxylic acid component, 80mol % ethylene glycol and 20 mol % bisphenol A ethylene oxide additiveas the diol component were copolymerized, was employed as thethermoplastic resin B. The results of the glass scattering preventiontest for the obtained film were passed. The obtained results are shownin Table 5.

TABLE 5 EXAMPLE EXAMPLE EXAMPLE EXAMPLE UNIT 21 22 23 24 COMPONENTSTHERMO- NAME OF — PET PET PET PET PLASTIC RESIN RESIN A INTRINSIC — 0.80.8 0.8 0.8 VISCOSITY Tg ° C. 81 81 81 81 THERMO- NAME OF — PETG PETGPETG PETG PLASTIC RESIN 9921 6763 6763 6763 RESIN B Tg ° C. 82 81 81 81SURFACE LAYER — — EASY- EASY- EASY- ADHESIVE ADHESIVE ADHESIVE LAYERLAYER LAYER LAYERING No. OF LAYERS — 7 33 33 33 LAYERING RATIO A/B — 5 55 5 FILM THICKNESS μm 150 150 100 100 FILM STRETCHING MD TIMES 3.2 3.23.2 3.2 FORMATION TD TIMES 3.3 3.3 3.3 3.3 HEAT TREATMENT ° C. 150 150150 230 TEMPERATURE PHYSICAL TRANSMITTANCE OF % 92 92 93 93 PROPERTIESALL LIGHT RAYS OF FILM HAZE % 2 2 1 1 TEAR STRENGTH mN 10000 26700 2500012000 IMPACT STRENGTH J 13 14 14 14 FACE-IMPACT STRENGTH J/mm 31 30 3020 EXAMPLE EXAMPLE EXAMPLE 25 26 27 COMPONENTS THERMO- NAME OF PET PETPET PLASTIC RESIN RESIN A INTRINSIC 0.8 0.8 0.8 VISCOSITY Tg 81 81 81THERMO- NAME OF PETG PE • BPA- PE • BPA- PLASTIC RESIN 6763 EO/T (10 mol%) EO/T (20 mol %) RESIN B Tg 81 79 78 SURFACE LAYER EASY-ADHESIVE EASY-EASY- LAYER, ADHESIVE ADHESIVE ANTI- LAYER LAYER REFRECTIVE LAYER, HARDCOAT LAYER, ADHESIVE LAYER LAYERING No. OF LAYERS 33 33 33 LAYERINGRATIO A/B 5 5 5 FILM THICKNESS 100 100 100 FILM STRETCHING MD 3.2 3.23.2 FORMATION TD 3.3 3.3 3.3 HEAT TREATMENT 150 150 150 TEMPERATUREPHYSICAL TRANSMITTANCE OF 93 93 93 PROPERTIES ALL LIGHT RAYS OF FILMHAZE 1 1 1 TEAR STRENGTH 25000 5210 6120 IMPACT STRENGTH 14 13 15FACE-IMPACT STRENGTH 27 25 28 Tg: GLASS TRANSITION TEMPERATURE MD:LONGITUDINAL DIRECTION OF FILM TD: WIDTH DIRECTION OF FILM IMPACTSTRENGTH: IMPACT ABSORPTION ENERGY

COMPARATIVE EXAMPLE 3

A drawn film was obtained as with Comparative Example 1 except that thedischarge was adjusted such that the film thickness was 100 μm, the filmwas stretched in the longitudinal direction, following which the bothsides of the film were subjected to corona discharge treatment in theatmosphere, wet tension of a base film was set to 55 mN/m, and theprocessing face thereof was applied with a coating fluid for formingfilm layers made up of polyester/melamine cross-linking agent/silicaparticles of mean particle diameter of 140 nm. The results of the glassscattering prevention test for the obtained film were not satisfactory,and the hardened-glass falling-ball test was also unsatisfactory sincethe rigid sphere passed through the obtained glass. The evaluationresults of the obtained film are shown in Table 6.

COMPARATIVE EXAMPLE 4

A film having film thickness of 100 μm was obtained as with Example 22except that the discharge was adjusted such that the film thickness was100 μm, copolymer polyester (hereafter, referred to as “PET/S”) (glasstransition temperature of 2° C., Young's modulus of 85 MPa) in whichsebacic acid of 40 mol % and terephthalic acid of 60 mol % asdicarboxylic acid components, ethylene glycol of 100 mol % as diolcomponents were copolymerized, was employed as the thermoplastic resinB, an anti-reflective layer and a hard coat layer having pencil hardnessof 4 H were provided on one face of the obtained film, and an adhesivelayer was provided on the other face of the obtained film. Thehardened-glass falling-ball test was unsatisfactory since the rigidsphere passed through the obtained glass. The evaluation results of theobtained film are shown in Table 6.

TABLE 6 COMPARATIVE COMPARATIVE UNIT EXAMPLE 3 EXAMPLE 4 COMPONENTSTHERMO- NAME OF — PET PET PLASTIC RESIN RESIN A INTRINSIC — 0.8 0.8VISCOSITY Tg ° C. 81 81 THERMO- NAME OF — — PET/S PLASTIC RESIN (40 mol%) RESIN B Tg ° C. — 2 SURFACE LAYER — EASY- EASY-ADHESIVE ADHESIVELAYER, LAYER ANTI- REFRECTIVE LAYER, HARD COAT LAYER, ADHESIVE LAYERLAYERING No. OF LAYERS — — 33 LAYERING RATIO A/B — — 5 FILM THICKNESS μm100 100 FILM STRETCHING MD TIMES 3.2 3.2 FORMATION TD TIMES 3.3 3.3 HEATTREATMENT ° C. 150 150 TEMPERATURE PHYSICAL TRANSMITTANCE OF % 93 88PROPERTIES ALL LIGHT RAYS OF FILM HAZE % 1 4 TEAR STRENGTH mN 1030 24000IMPACT STRENGTH J 5 7 FACE-IMPACT J/mm 7 17 STRENGTH Tg: GLASSTRANSITION TEMPERATURE MD: LONGITUDINAL DIRECTION OF FILM TD: WIDTHDIRECTION OF FILM

INDUSTRIAL APPLICABILITY

In the event of applying a glass protecting film onto glass, the filmhas high transparency, and also has high face-impact resistance whichcan endure great impact strength applied to the glass. Accordingly, theglass protecting film is effectively employed as a display glassprotecting film for CRT displays which need to have high transparencyand also cause huge explosions at the time of glass being subjected todamage, or liquid crystal displays, plasma displays, organic ELdisplays, field emission displays, and so forth, wherein it is necessaryto protect the expensive display devices. Also, the glass protectingfilm protects glass from disasters such as typhoons, is hardly damaged,and is capable of drastically preventing glass scattering due to damage,and accordingly is effectively employed as a windowpane protecting filmfor structures such as public facilities, houses, or large buildings,automobiles, HST (High-Speed Trains), and electric trains.

1. A glass protecting film, comprising a multi-layer structure whichcomprises at least two kinds of thermoplastic resin of which thedifference in glass transition temperature is 40° C. or lower, in whichface-impact strength is 18 J/mm or more, in which haze is 3% or less andtearing-propagation resistance in the longitudinal and/or widthdirection is 10 N/mm or more.
 2. A glass protecting film, comprising amulti-layer structure which comprises at least, two kinds ofthermoplastic resin of which difference in glass transition temperatureis 40° C. or lower, in which impact strength is 8 to 40 J, in which hazeis 3% or less and tearing-propagation resistance in the longitudinaland/or width direction is 10 N/mm or more.
 3. The glass protecting filmaccording to claim 1 or claim 2, in which the glass transitiontemperature of thermoplastic resin which is comprised in the film is 50°C. or higher.
 4. The glass protecting film according to claim 1 or claim2, further comprising a layer in which at least one kind ofthermoplastic resin of the thermoplastic resins comprises polyesterhaving 1,4-cyclohexane dimethanol as one of the components.
 5. The glassprotecting film according to claim 4, in which the amount ofcopolymerization of 1,4-cyclohexane dimethanol is 20 to 50 mol %.
 6. Theglass protecting film according to claim 4, in which the amount ofcopolymerization of 1,4-cyclohexane dimethanol is 30 to 40 mol %.
 7. Theglass protecting film according to claim 1 or claim 2, in which at leastone kind of thermoplastic resin of the thermoplastic resins comprisesthermoplastic resin having 2,2-bis (4′-β-hydroxyethoxyphenyl) propanegroup.
 8. The glass protecting film according to claim 1 or claim 2, inwhich thermoplastic resin which is comprised in each layer has a tensileelastic modulus of 1400 MPa or more.
 9. The glass protecting filmaccording to claim 1 or claim 2, in which a layer structure is amulti-layer structure of 8 to 256 layers.
 10. The glass protecting filmaccording to claim 1 or claim 2, satisfying the following formula (1)Film thickness: T (μm)Number of total layers: L1.2≦T/L≦30  (1).
 11. The glass protecting film according to claim 1 orclaim 2, in which the thickness of a layer which comprises polyesterhaving 1,4-cyclohexane dimethanol as one of the components is 0.05 to 30μm.
 12. The glass protecting film according to claim 1 or claim 2, inwhich film thickness is 10 to 500 μm.
 13. The glass protecting filmaccording to claim 1 or claim 2, further comprising an adhesive layer onat least one face thereof.
 14. The glass protecting film according toclaim 1 or claim 2, further comprising an anti-reflective layer on atleast one, face thereof.
 15. A glass protecting film according to claim1 or claim 2, further comprising a hard coat layer on at least one facethereof.
 16. The glass protecting film according to claim 1 or claim 2,wherein pencil hardness of at least one face thereof is 2H or more. 17.The glass protecting film according to claim 1 or claim 2, in whichtransmittance of near-infrared rays is 20% or less.
 18. The glassprotecting film according to claim 1 or claim 2, in which transmittanceof visible light is 70% or more.
 19. The glass protecting film accordingclaim 1 or claim 2, in which transmittance of visible light is 80% ormore.
 20. The glass protecting film according to claim 1 or claim 2, inwhich transmittance of visible light is 90% or more.
 21. The glassprotecting film according to claim 1 or claim 2, wherein tensileelongation at break of at least one direction of the longitudinal andwidth directions is 100 to 300%, and tensile stress at break is 120 to400 MPa.
 22. The glass protecting film according to claim 1 or claim 2,in which the glass protecting film is stretched in at least onedirection.
 23. The glass protecting film according to claim 1 or claim2, in which the glass protecting film is applied onto the front face ofa flat display.
 24. The glass protecting film according to claim 23, inwhich the flat display is a flat CRT display.